in Vol. 4 - March Issue - Year 2003
The somewhat different Cartridge Filter
The operator can replace the filter cartridge easily and quickly.
A view of the new cartridge filter unit, which offers optimum routing of air.
The new cartridge filter system is shown here in a roller-conveyor blasting unit
An additional advantage: During filter changes, the load-bearing metal body of the filter cartridge is reusable. Only the paper material is replaced.
A new cartridge filter system developed especially for blast machinery is designed to significantly increase process safety. According to the manufacturer, the system is low in maintenance and especially economical to operate.
The new cartridge filter systems use a current of air to initially extract the dust particles created by the blasting process. The air flows through the impact separator, where the initial separation of heavy dust particles occurs. After this, dust enters the lower filter chamber, where the filter cartridges are located. Dust is removed from the air as it passes through the filter cartridges and the clean air then flows upward into the clean gas chamber.
The filter cartridges are simultaneously cleaned in programmable intervals using pulses of compressed air delivered from compressed air nozzles located above the cartridges. This loosens dust from the filter walls. The dust particles are fed to a hopper located beneath the filter, where they are collected in a dust collection container made of metal or paper.
Clean air is released to the outside environment through openings in the side of the upper filter housing. In the event that a filter cartridge is destroyed, additional filter inserts collect the dust until the damage is repaired.
Special Filter Cartridges
Starting with the fact that filter cartridges must do a good job of absorbing dust, but should still save energy and be able to be cleaned completely, the AGTOS company chose a conical shape for the cartridges when developing the new filter system. This permits the compressed air impulse to more directly impact the inside of the sidewalls and the attached coating of dust.
In comparison to other filter cartridges, the overall area of the filter surface is smaller. And there is good reason for this. The special structure of the paper or polyester fabric makes it possible to draw more air per m2 through the cartridge. The use of a rougher fold provides for better dust adhesion and cleaning because the dust is dislodged more easily by the compressed air impulse.
Environmentally Friendly and Cost-Saving
In comparison to the smooth sidewalls of conventional filter cartridges, the conical shape of the filter cartridges alone is enough to achieve a better utilization of the compressed air pulses. In addition, the inner volume of the cartridges is less that that of cylindrical cartridges, a feature that increases the effectiveness of the compressed air pulses.
The disposal process illustrates yet another positive design advantage of the cartridges. The load-bearing metal body is reusable. Only the paper or polyester wrapping requires disposal. Depending on the type of dust collected, this wrapping can usually be burned or disposed of as common industrial waste. This eliminates additional disposal costs.
The right Filter Material for the Job
Standard applications use so-called paper filter cartridges that are manufactured in an environmentally friendly manner from unbleached cellulose. These cartridges are characterized by good filtration efficiency when dealing with fine dust particles and can be easily cleaned. Filter cartridges equipped with polyester fabric are used to collect ultra-fine dust particles in applications where air inflow velocities are high. These cartridges also exhibit high stability and excellent wet strength.
Replacing filter cartridges is often extremely time-consuming and can also be dangerous to one’s health because dust is involved. This was something taken into account by the engineering team at AGTOS.
Newly developed slide-in inserts simplify the exchange and replacement of cartridges. The cartridges are pulled from the filter unit and can then be replaced outside the filter in a clean environment. The cartridges are still precisely positioned when reinserted and always installed with the proper contact pressure.
Reprinted with the kind permission of JOT (Journal für Oberflächentechnik).
At one Glance
The Advantages of the Filter Unit
a) The new filter cartridges have a conical shape that distinguishes them from those of other manufacturers. The conical shape ensures the optimum routing of air. The intensity of the compressed air blast can be lowered and the filter material is protected.
b) During cleaning, dust dislodges more easily because of the filter cartridge’s wide-angle fold.
c) The filter unit can be equipped with a variety of dust collection containers: paper sacks, metal containers, big bags or dustbins.
d) An impact separator is integrated in the filter housing. It prevents coarse dust particles from damaging the filter cartridges.
e) By using an integrated secondary filter, residual dust levels < 1 mg are achieved. This makes it possible to re-circulate exhaust air into the workshop hall.
f) Depending on the application, cartridge filters are available in paper or polyester fabric.
g) Maintenance-friendly construction with large maintenance openings.
h) A quick release system makes it possible to exchange cartridges in a very short period of time. The system ensures that cartridges are always installed with the correct contact pressure in an absolutely centralized position.
i) Environmentally friendly, as less waste is created.